"Once More, With Feeling" was the seventh episode of the sixth season and the only episode performed as a musical. In this episode, a demon compels the people of Sunnydale to break into song and express hidden truths and Buffy confesses that she had been in heaven when Willow brought her back from the dead.

During season five, Dawn, Buffy's younger sister, suddenly appears out of nowhere. Although she is new to the series, to the characters it's as if she has always been there. It is later discovered that Dawn was created as a "Key" in human form that has the potential to unlock a Hell dimension.

Ryan Reynolds was offered the role of Xander but reportedly turned it down because he couldn't bear to relive his high school experience. According to Reynolds, "I love that show and I loved Joss Whedon ... but my biggest concern was that I didn't want to play a guy in high school. I had just come out of high school and it was f***ing awful."

According to Cordelia, The Bronze is "...the only club worth going to around here. They let anybody in, but it's still the scene. It's in the bad part of town."

James Marsters received the scar on his left eyebrow during a mugging in New York, and the scar was even worked into Spike's vampire face prosthetic.

In order to collect a sacrifice of newborn babies for the demon Lucronis, Mr. Trick has the band candy cursed to dull the adults' senses and cause them to act like irresponsible teenagers.

Carpenter, who played 16-year-old Cordelia, was 27 years old when Buffy first aired.

Marsters originally auditioned with a Texas twang but then the character was changed to a Brit. Anthony Head coached Marsters on his English accent.

Alyson Hannigan is the only member of the "Scooby Gang" that wasn't in the unaired pilot, a 25 minute production used to pitch the series to the networks. Willow was played by Riff Regan who was recast for the series at the request of the studio.

David Boreanaz would often pull down his pants while other cast members were filming to see if they could hold a straight face.